1. Field of the Invention
The present invention relates to a semiconductor device and a power receiving device. In particular, the present invention relates to a semiconductor device and a power receiving device that transmit and receive data through a radio wave and wirelessly receive electric power.
2. Description of the Related Art
In recent years, an individual identification technology utilizing wireless communication such as radio waves or electromagnetic waves has attracted attention. In particular, as a semiconductor device which transmits and receives data by wireless communication, an individual identification technology utilizing an RFID (Radio Frequency Identification) tag has attracted attention. The RFID tag is also referred to as an IC (Integrated Circuit) tag, an IC chip, an RF (Radio Frequency) tag, a wireless tag, or an electronic tag. The individual identification technology utilizing an RFID tag or the like has started to be utilized for production, management, individual identification, or the like of individual objects.
RFID tags can be broadly classified into two types depending on whether a power supply is incorporated therein or power supply voltage is supplied from outside, that is, an active-type RFID tag incorporating a power supply capable of transmitting radio waves or electromagnetic waves including information on the RFID tag, and a passive-type RFID tag which is driven with the utilization of electric power of radio waves or electromagnetic waves (carrier waves) from outside (as for the active-type RFID, see Patent Document 1: Japanese Published Patent Application No. 2005-316724 and as for the passive-type RFID, see Patent Document 2: Japanese Translation of PCT International Application No. 2006-503376). Of them, the active-type RFID tag incorporates a power supply for driving the RFID tag and includes a battery as the power supply. As for the passive-type RFID tag, a structure is realized in which power supply voltage for driving the RFID tag is generated with the utilization of electric power of radio waves or electromagnetic waves (carrier waves) from outside and a battery is not provided.
FIG. 3 is a block diagram illustrating a specific structure of an active-type RFID tag (semiconductor device 3100). In the active-type semiconductor device 3100 shown in FIG. 3, a signal received by an antenna circuit 3101 is inputted to a demodulation circuit 3105 and an amplifier 3106 in a signal processing circuit 3102. A communication signal is usually transmitted after carrier waves with 13.56 MHz or 915 MHz are processed by ASK modulation or PSK modulation. It is to be noted that, in ASK modulation, a digital signal is expressed in difference in amplitude and modulated. In PSK modulation, a digital signal is expressed in difference in a phase of a carrier wave with a constant frequency and modulated. Here, an example of using a carrier wave with 13.56 MHz as a signal is described. In FIG. 3, a clock signal which functions as a reference is needed for processing the signal, and a carrier wave with 13.56 MHz is used as a clock signal. The amplifier 3106 amplifies the carrier wave with 13.56 MHz and supplies it to a logic circuit 3107 as a clock signal. In addition, the ASK-modulated signal or the PSK-modulated signal is demodulated by the demodulation circuit 3105. The demodulated signal is transmitted to the logic circuit 3107 to be analyzed. The signal analyzed by the logic circuit 3107 is transmitted to a memory control circuit 3108, a memory circuit 3109 is controlled by the memory control circuit 3108 based on this signal, and data stored in the memory circuit 3109 is extracted to be transmitted to the logic circuit 3110. The data is amplified by the amplifier 3111 after being encoded by the logic circuit 3110, and a carrier wave is modulated by the modulation circuit 3112 based on the signal. On the other hand, electric power of the semiconductor device 3100 in FIG. 3 is supplied through a power supply circuit 3104 by a battery 3103 provided outside the signal processing circuit 3102. Then, the power supply circuit 3104 supplies electric power to the amplifier 3106, the demodulation circuit 3105, the logic circuit 3107, the memory control circuit 3108, the memory circuit 3109, the logic circuit 3110, the amplifier 3111, the modulation circuit 3112, and the like.
FIG. 4 is a block diagram illustrating a specific structure of a passive-type RFID tag (semiconductor device 3200). In the passive-type semiconductor device 3200 shown in FIG. 4, a signal received by an antenna circuit 3201 is inputted to a demodulation circuit 3205 and an amplifier 3206 in a signal processing circuit 3202. A communication signal is usually transmitted after carrier waves with 13.56 MHz or 915 MHz are processed by ASK modulation or PSK modulation. Here, an example of using a carrier wave with 13.56 MHz as a signal is described. In FIG. 4, a clock signal which functions as a reference is needed for processing the signal, and a carrier wave with 13.56 MHz is used as a clock signal. The amplifier 3206 amplifies the carrier wave with 13.56 MHz and supplies it to a logic circuit 3207 as a clock signal. In addition, the ASK-modulated signal or the RSK-modulated signal is demodulated by the demodulation circuit 3205. The demodulated signal is transmitted to the logic circuit 3207 to be analyzed. The signal analyzed by the logic circuit 3207 is transmitted to a memory control circuit 3208, a memory circuit 3209 is controlled by the memory control circuit 3208 based on this signal, and data stored in the memory circuit 3209 is extracted to be transmitted to the logic circuit 3210. The data is amplified by the amplifier 3211 after being encoded by the logic circuit 3210, and a carrier wave is modulated by the modulation circuit 3212 based on the signal. On the other hand, electric power of the semiconductor device 3200 in FIG. 4 is supplied in such a manner that a signal inputted to a rectifier circuit 3203 is rectified and inputted to a power supply circuit 3204. Then, the power supply circuit 3204 supplies electric power to the amplifier 3206, the demodulation circuit 3205, the logic circuit 3207, the memory control circuit 3208, the memory circuit 3209, the logic circuit 3210, the amplifier 3211, the modulation circuit 3212, and the like.
On the other hand, various electronic devices are coming into wide use, and a wide variety of products are in the marketplace. In particular, in recent years, the spread of portable electronic devices has been marked. For example, mobile phones, digital video cameras, and the like have become very convenient because of high-definition display portions, increased durability of batteries, and further reduction in power consumption of the batteries. A portable electronic device has a structure in which a battery that is a power receiving means is incorporated as a power supply for driving the portable electronic device, and electric power is secured by the battery. As matters now stand, as a battery, a secondary battery (hereinafter referred to as a battery) such as a lithium ion battery is used, and the battery is charged from an AC adaptor which is plugged into a household AC power supply that is a power supply means (see Patent Document 3: Japanese Published Patent Application No. 2005-150022).
It is to be noted that an electronic device provided with a battery includes a bicycle, a motor vehicle (including electric vehicles and other transportation devices driven by electric power regardless of four-wheel vehicles or two-wheel vehicles), or the like that is a transportation device.